Wet blasting is a cleaning process that uses liquid to enhance a surface’s finish levels. Though it was created to mitigate the ban on silica in sand blasting, it has remained a popular finishing method due to its many advantages over the previously used method of sand blasting. However, with wet blasting systems, the abrasive and water mix is more gentle on the part surface because the water acts as a cushion.

Water acts as a buffer in the lubrication of these abrasive particles, resulting in an even flow across the surface. As a result, blasting on a delicate part can be done quickly and easily with a reduced chance of damaging the substrate. The abrasive action is consistent across the surface for an even finish.

Industrial uses for wet grit blasting include:

• General cleaning: Wet blasting can be used to clean many surfaces.
• Deflashing: Wet blasting will remove flash, the excess material on a cast, molded or forged product.
• Descaling: Water blasting removes scale and burrs without damaging the substrate material.
• Surface preparation: This process can prepare a surface for a bonding coating or hard chrome coating. It can also provide surface texturizing for a final coating.
• Remanufacturing: Wet blasting works extremely well in remanufacturing.

In a pressure blast machine, the abrasive media is contained in a pressure vessel under pressure (at 40 to 100 psi) for use in the process. Examples of this abrasive media include steel shot or grit. Once the valve is open to start blasting, the media moves from the pressure pot through the grit valve and then through the hose to start blasting under pressure using the gun or nozzle. The media has two-to-three-times times the velocity on impact and would be close to three-times faster with stripping applications. Normal blasting pressure ranges from 35 to 45 psi.

The pressure blaster is also helpful when you need to complete the blasting process quickly. It moves three times faster than a comparable suction-based blaster cabinet.

A pressure blast cabinet is an ideal tool for removing contaminants, powder coating or heavy-duty layers of paint. The unique combination of air and abrasive media cuts, etches, abrades, cleans or otherwise changes the condition of the surface of your target piece. The process is a high-quality method of surface preparation.

The pressure blasting process offers several benefits:

• Control: Pressure blasting with an abrasive is ideal for preparing a surface. This process is the most thorough approach to cleaning metal. It creates an etched surface perfect for an excellent finish.
• Irregularities: The blasting process also gives the user access to clean the hard-to-reach spots of irregularly shaped parts.
• Applications: Beyond metal applications, a pressure blaster can etch glass, carve designs in wood or stone, harden manufactured parts and much more.

The pressure blast cabinet is a go-to solution when you need a heavy-duty tool that can move quickly and handle large quantities. That’s why the Advanced Deburring & Finishing team recommends these machines when you need to remove layers or want to smooth a rough surface at a rapid pace.

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Passivation is a chemical process that uses a mild oxidizing agent, such as a mineral or organic acid solution, to promote the removal of excess iron from the surface of the stainless steel. This treatment will enhance the formation of a chromic oxide layer, thereby enhancing its corrosion-resistant properties.

Why Use a Passivation Machine?

Passivation is an essential process for making stainless steel rust-resistant. The process has been a best practice for steel production since the 1900s because of its ability to:

• Create a chemical barrier against rust.
• Extend the steel’s life span.
• Remove harmful contaminants from a piece’s surface.

How Does a Passivation System Work?

As an iron-based alloy, stainless steel consists of iron, chromium and nickel. The corrosion-resistant properties of stainless steel come from its chromium content. When exposed to oxygen, the chromium transforms into a layer of chromium oxide that protects the steel from rust.

Passivation works by immersing stainless steel parts into an acid bath that dissolves the surface’s iron particles while maintaining the chromium content. Removing the iron with acid allows the steel to develop a surface higher in chromium than the underlying steel.

Once you remove the stainless steel from its acid bath, oxygen reacts to the chromium-rich surface and forms a thick layer of protective chromium oxide. This thicker layer drastically reduces the risk of corrosion and extends the part’s life span.

Since the metalworking industry has a wide variety of finishing requirements and an equally wide range of products to be finished, the efforts necessary to accomplish the desired results demand increasing degrees of specialization. Equipment that meets your precise operating needs is crucial to satisfying the specific output standards for the final product.

The spindle concept is sometimes referred to as a Slurry Deburring Machine or Flowing Abrasive Machine. The equipment generally includes a circular rotating tub holding loose media/abrasive, a rotary spindle to hold parts and fixturing.

The principle of this process is to use slurry deburring to finish a workpiece mounted on the rotary spindle by immersing it into a rapidly moving abrasive slurry. The velocity of the abrasive is generated by the rotating tub speed suitable for the process requirements. The abrasive slurry particles swiftly flow over and through holes and rough edges, removing sharpness and burrs.

If you’re new to doing your own surface finishing, you may be confused about the different types of media available, particularly the role of plastic tumbling media. In what situation would you use a plastic rather than something like steel or ceramic media?

Plastic media came about to finish softer metals/alloys. Processing softer metals (i.e. aluminum, brass, bronze, etc.) The other media are heavier per cubic foot, then the concern is rolling over the burr and peening against the surface. Much harder and longer cycle times are needed to remove a peened down burr. If the burr is a parent metal it would not be a burr as identified with vibratory finishing/deburring.

If your industrial products are mostly tough steel, cast iron, and stainless products, you may want to try using a ceramic bond. However, plastic tumbling media can be just as aggressive as ceramic and even faster with cutting. The issue then is the attrition rate or rate that the media wears away. It is more costly, wears faster, and has more residue to deal with, but can provide a very nice surface profile and RA/RMS. There can be safe scrubbing action to remove deposits and build upon a plastic part surface. Deflashing or deburring plastic is a different story. All pre-made tumbling media is manufactured to wear away at a certain rate (attrition rate/how long is going to last in the machine?). The faster it wears away to more waste is generated from the process.

What Are the Benefits of Using Plastic Media Blasting for Your Parts Finishing?

The main advantage of using plastic abrasive blasting media is that it’s easier on your more sensitive surfaces and does not change the original metal surface profile under the paint.

Benefit: Not having to refinish the metal substrate prior to repainting. The finer the surface substrate with the finish the better the paint quality/appearance with the end result. The four types of plastic blasting media. Acrylic, melamine, polyester, and urea. All have their advantages and applications.   The plastic media blasting process is a dry process, meaning no warping, pitting or flash rust. Dust collection is so very important today. The right collectors are needed for any blasting process. Plastic media blasting does have some special features over a standard blast unit to be able to move abrasive through the system without them clogging up. Plastic media blasting is very susceptible to moisture build-up.

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